"Minutes and seconds of the day"
Translation:Günün dakikaları ve saniyeleri
The possessive is required here. 'Gün' is 'day', whereas 'günün' means 'the day's...' so the object after it needs to be adjusted to show that it belongs to the day. So 'dakikalar' becomes 'dakikaları' and 'saniyeler' becomes 'saniyeleri'. The -ı/i suffix shows that the minutes and seconds belong to the day. Another example would be 'benim elmalarım' 'onun elmaları' - here the -ım suffix shows that the apples belong to me, 'my apples' and the '-ı' suffix shows that the apples belong to him/her, 'his/her apples'. I hope this helps.